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/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
#include "cookie.h"
#include "peer.h"
#include "device.h"
#include "messages.h"
#include "ratelimiter.h"
#include "crypto/blake2s.h"
#include "crypto/chacha20poly1305.h"
#include <linux/jiffies.h>
#include <net/ipv6.h>
#include <crypto/algapi.h>
void cookie_checker_init(struct cookie_checker *checker, struct wireguard_device *wg)
{
init_rwsem(&checker->secret_lock);
checker->secret_birthdate = get_jiffies_64();
get_random_bytes(checker->secret, NOISE_HASH_LEN);
checker->device = wg;
}
enum { COOKIE_KEY_LABEL_LEN = 8 };
static const u8 mac1_key_label[COOKIE_KEY_LABEL_LEN] = "mac1----";
static const u8 cookie_key_label[COOKIE_KEY_LABEL_LEN] = "cookie--";
static void precompute_key(u8 key[NOISE_SYMMETRIC_KEY_LEN], const u8 pubkey[NOISE_PUBLIC_KEY_LEN], const u8 label[COOKIE_KEY_LABEL_LEN])
{
struct blake2s_state blake;
blake2s_init(&blake, NOISE_SYMMETRIC_KEY_LEN);
blake2s_update(&blake, label, COOKIE_KEY_LABEL_LEN);
blake2s_update(&blake, pubkey, NOISE_PUBLIC_KEY_LEN);
blake2s_final(&blake, key, NOISE_SYMMETRIC_KEY_LEN);
}
/* Must hold peer->handshake.static_identity->lock */
void cookie_checker_precompute_device_keys(struct cookie_checker *checker)
{
if (likely(checker->device->static_identity.has_identity)) {
precompute_key(checker->cookie_encryption_key, checker->device->static_identity.static_public, cookie_key_label);
precompute_key(checker->message_mac1_key, checker->device->static_identity.static_public, mac1_key_label);
} else {
memset(checker->cookie_encryption_key, 0, NOISE_SYMMETRIC_KEY_LEN);
memset(checker->message_mac1_key, 0, NOISE_SYMMETRIC_KEY_LEN);
}
}
void cookie_checker_precompute_peer_keys(struct wireguard_peer *peer)
{
precompute_key(peer->latest_cookie.cookie_decryption_key, peer->handshake.remote_static, cookie_key_label);
precompute_key(peer->latest_cookie.message_mac1_key, peer->handshake.remote_static, mac1_key_label);
}
void cookie_init(struct cookie *cookie)
{
memset(cookie, 0, sizeof(struct cookie));
init_rwsem(&cookie->lock);
}
static void compute_mac1(u8 mac1[COOKIE_LEN], const void *message, size_t len, const u8 key[NOISE_SYMMETRIC_KEY_LEN])
{
len = len - sizeof(struct message_macs) + offsetof(struct message_macs, mac1);
blake2s(mac1, message, key, COOKIE_LEN, len, NOISE_SYMMETRIC_KEY_LEN);
}
static void compute_mac2(u8 mac2[COOKIE_LEN], const void *message, size_t len, const u8 cookie[COOKIE_LEN])
{
len = len - sizeof(struct message_macs) + offsetof(struct message_macs, mac2);
blake2s(mac2, message, cookie, COOKIE_LEN, len, COOKIE_LEN);
}
static void make_cookie(u8 cookie[COOKIE_LEN], struct sk_buff *skb, struct cookie_checker *checker)
{
struct blake2s_state state;
if (!time_is_after_jiffies64(checker->secret_birthdate + COOKIE_SECRET_MAX_AGE)) {
down_write(&checker->secret_lock);
checker->secret_birthdate = get_jiffies_64();
get_random_bytes(checker->secret, NOISE_HASH_LEN);
up_write(&checker->secret_lock);
}
down_read(&checker->secret_lock);
blake2s_init_key(&state, COOKIE_LEN, checker->secret, NOISE_HASH_LEN);
if (skb->protocol == htons(ETH_P_IP))
blake2s_update(&state, (u8 *)&ip_hdr(skb)->saddr, sizeof(struct in_addr));
else if (skb->protocol == htons(ETH_P_IPV6))
blake2s_update(&state, (u8 *)&ipv6_hdr(skb)->saddr, sizeof(struct in6_addr));
blake2s_update(&state, (u8 *)&udp_hdr(skb)->source, sizeof(__be16));
blake2s_final(&state, cookie, COOKIE_LEN);
up_read(&checker->secret_lock);
}
enum cookie_mac_state cookie_validate_packet(struct cookie_checker *checker, struct sk_buff *skb, bool check_cookie)
{
u8 computed_mac[COOKIE_LEN];
u8 cookie[COOKIE_LEN];
enum cookie_mac_state ret;
struct message_macs *macs = (struct message_macs *)(skb->data + skb->len - sizeof(struct message_macs));
ret = INVALID_MAC;
compute_mac1(computed_mac, skb->data, skb->len, checker->message_mac1_key);
if (crypto_memneq(computed_mac, macs->mac1, COOKIE_LEN))
goto out;
ret = VALID_MAC_BUT_NO_COOKIE;
if (!check_cookie)
goto out;
make_cookie(cookie, skb, checker);
compute_mac2(computed_mac, skb->data, skb->len, cookie);
if (crypto_memneq(computed_mac, macs->mac2, COOKIE_LEN))
goto out;
ret = VALID_MAC_WITH_COOKIE_BUT_RATELIMITED;
if (!ratelimiter_allow(skb, dev_net(checker->device->dev)))
goto out;
ret = VALID_MAC_WITH_COOKIE;
out:
return ret;
}
void cookie_add_mac_to_packet(void *message, size_t len, struct wireguard_peer *peer)
{
struct message_macs *macs = (struct message_macs *)((u8 *)message + len - sizeof(struct message_macs));
down_write(&peer->latest_cookie.lock);
compute_mac1(macs->mac1, message, len, peer->latest_cookie.message_mac1_key);
memcpy(peer->latest_cookie.last_mac1_sent, macs->mac1, COOKIE_LEN);
peer->latest_cookie.have_sent_mac1 = true;
up_write(&peer->latest_cookie.lock);
down_read(&peer->latest_cookie.lock);
if (peer->latest_cookie.is_valid && time_is_after_jiffies64(peer->latest_cookie.birthdate + COOKIE_SECRET_MAX_AGE - COOKIE_SECRET_LATENCY))
compute_mac2(macs->mac2, message, len, peer->latest_cookie.cookie);
else
memset(macs->mac2, 0, COOKIE_LEN);
up_read(&peer->latest_cookie.lock);
}
void cookie_message_create(struct message_handshake_cookie *dst, struct sk_buff *skb, __le32 index, struct cookie_checker *checker)
{
struct message_macs *macs = (struct message_macs *)((u8 *)skb->data + skb->len - sizeof(struct message_macs));
u8 cookie[COOKIE_LEN];
dst->header.type = cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE);
dst->receiver_index = index;
get_random_bytes_wait(dst->nonce, COOKIE_NONCE_LEN);
make_cookie(cookie, skb, checker);
xchacha20poly1305_encrypt(dst->encrypted_cookie, cookie, COOKIE_LEN, macs->mac1, COOKIE_LEN, dst->nonce, checker->cookie_encryption_key);
}
void cookie_message_consume(struct message_handshake_cookie *src, struct wireguard_device *wg)
{
u8 cookie[COOKIE_LEN];
struct index_hashtable_entry *entry;
bool ret;
entry = index_hashtable_lookup(&wg->index_hashtable, INDEX_HASHTABLE_HANDSHAKE | INDEX_HASHTABLE_KEYPAIR, src->receiver_index);
if (unlikely(!entry))
return;
down_read(&entry->peer->latest_cookie.lock);
if (unlikely(!entry->peer->latest_cookie.have_sent_mac1)) {
up_read(&entry->peer->latest_cookie.lock);
goto out;
}
ret = xchacha20poly1305_decrypt(cookie, src->encrypted_cookie, sizeof(src->encrypted_cookie), entry->peer->latest_cookie.last_mac1_sent, COOKIE_LEN, src->nonce, entry->peer->latest_cookie.cookie_decryption_key);
up_read(&entry->peer->latest_cookie.lock);
if (ret) {
down_write(&entry->peer->latest_cookie.lock);
memcpy(entry->peer->latest_cookie.cookie, cookie, COOKIE_LEN);
entry->peer->latest_cookie.birthdate = get_jiffies_64();
entry->peer->latest_cookie.is_valid = true;
entry->peer->latest_cookie.have_sent_mac1 = false;
up_write(&entry->peer->latest_cookie.lock);
} else
net_dbg_ratelimited("%s: Could not decrypt invalid cookie response\n", wg->dev->name);
out:
peer_put(entry->peer);
}
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